My non-enthusiast brother asked for some car advice. I don’t know much about normal-people cars so E39 M5 is not in the cards. He’s looking for mid-size, say, E Class or 5 Series size with AWD. What do you suggest?

Lexus GS
Acura TL (used) or TLX (new or used)
Jaguar XF
Audi A6/S6
Cadillac CTS
Genesis Sedan w/ HTRAC (don't knock it 'til you try it - great bargain, at used prices, if comfort and easy speed are your thing and the badge isn't nearly as important). Up here in Canada, we can get it with a 5.0L V8 and AWD but the US only gets AWD with the 3.8L V6, apparently.

You could also try for a Kia Stinger GT or something like that, which has a pretty nice interior, looks great and drives quite well. It's "luxury" in the sense that it has all the bells and whistles but the badge is hardly "luxury".

I have had a trouble free BMW 3 series (knock on wood) for the first 42,000 miles, and it has the BEST AWD I have ever had in bad weather. It goes through snow and ice like a champ on decent all seasons and seems to outdo any SUVs I come across in the snow. But if he is looking used BMW and checks out the 4cyl instead of the 6, make sure it is 2015 or newer as they corrected a timing chain flaw starting in 2015. Actually late late in the 2014 model year, but hard to tell finding the build date in the door or looking up the vin.

Repair bills are real too. My sister had a 2013 Q7 that got lemon'ed in 2015 and replaced with a (then) current model year. The SUV recently went out of warranty and like clock work is experiencing a myriad of issues including heavy oil consumption. Bro in-law didn't learn the lesson from their purchase with the Q7 and got a 2015 A4 2.0 that has already required repair and maintenance beyond basic fluid and air/cabin filter changes.

My direct family (parents and siblings w/spouses) have owned 8 Mercedez Benz, 7 BMWs, 3 Audis, and 2 Range Rovers since 1985. With the exception of the 2017 Audi S3 and 2018 MB C43 (since they're essentially still brand new), none of them have been anywhere remotely close to Japanese level of reliability.

FWIW, they're all very particular about outward appearances and prestige.

I drive a Subaru and a Honda - my wife has a Toyota... I'm the only Japanese car owner in the family.

Edit: Should also echo that the family mechanic says that Audis are the worst to wrench on from a design standpoint - engine bay is cramped and components are poorly placed such that replacement/repair requires a lot of labor removing things that hinder access.

I have good luck with Lexus, my DD is a 96 LS400 with over 220K miles. Still going strong with just regular maintenance like oil, tires, filters etc. Keeping my eyes open for another LS in a year or two. Car is pretty heavy so I have no problem driving it in the snow with the four seasons tire, I prefer it over the front wheel drive Volvo.